I'm building a motor for my truck. I know this is the wrong place but i'm using a L98 heads. What is the power limitations of these heads? I'm using these in place of the swirl port heads that came factory on my truck motor. The L98's look to have been nicely ported but I dont have another set of heads to compare. No sharp edges....all smooth and very rounded. I'm looking for 350 hp at the flywheel? Will these heads support that number.

 

The intake was a bigger limiting factor for the L98. I would think that 350hp at the flywheel shouldn't be a problem...

 

John Lingenfelter always felt the L98 heads could support 400-425hp with their CNC port job and one of his mild roller cams.. Definately with something better than a TPI intake setup also.

 

John Millican posted a few dyno results from an LT1 intake swap with all the bolt-ons and a cam. That guy pulled 300rwhp out of his car with stock heads. I admit the engine was FAR from stock though.

However, stock heads are stock heads.

 

what are the limits of the stock valve springs? Is .480 ok?

 

I think I've read that they top out about .470 or .475" lift. Not sure exactly, but best to be sure before putting a big camshaft in. I'd call up a company like Comp Cams and see what they recomend. They may have a spring set you can drop in without cutting the heads.

FYI, I ran .460" lift on my L98 with no problems. Just an L98 cam with 1.6rr's.